Dave Hansen wrote:

quoted

+                       if (zone->nr_mem_map > 1) {
+                               /*
+                                * there may be hole in zone's memmap &&
+                                * hole is not aligned in this order.
+                                * currently, I think CONFIG_VIRTUAL_MEM_MAP
+                                * case is only case to reach here.
+                                * Is there any other case ?
+                                */
+                               /*
+                                * Is there better call than pfn_valid ?
+                                */
+                               if (!pfn_valid(zone->zone_start_pfn
+                                              + (page_idx ^ (1 << order))))
+                                       break;
+                       }

Nice try.  How about putting the ia64 code in a macro or header function
that you can #ifdef out on all the other architectures?  We used to be
able to see that entire while loop on one screen.  That's a bit harder
now.  

Currently, I think zone->nr_mem_map itself is very vague.
I'm now looking for another way to remove this part entirely.

I think mem_section approarch may be helpful to remove this part,
but to implement full feature of CONFIG_NONLINEAR,
I'll need lots of different kind of patches.
(If mem_map is guaranteed to be contiguous in one mem_section)

1. Now, I think some small parts, some essence of mem_section which
   makes pfn_valid() faster may be good.

And another way,

2. A method which enables page -> page's max_order calculation
   may be good and consistent way in this no-bitmap approach.

But this problem would be my week-end homework :).

--Kame

-- 
--the clue is these footmarks leading to the door.--
KAMEZAWA Hiroyuki [off-list ref]

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